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SubjectRe: [PATCH v2 2/3] mtd: rawnand: stm32_fmc2: add STM32 FMC2 NAND flash controller driver
Hi Christophe,

On Fri, 5 Oct 2018 11:41:59 +0200
<christophe.kerello@st.com> wrote:

A few more comments.

> +/* Sequencer read/write configuration */
> +static void stm32_fmc2_rw_page_init(struct nand_chip *chip, int page,
> + int raw, bool write_data)
> +{
> + struct stm32_fmc2 *fmc2 = nand_get_controller_data(chip);
> + struct mtd_info *mtd = nand_to_mtd(chip);
> + u32 csqcfgr1, csqcfgr2, csqcfgr3;
> + u32 csqar1, csqar2;
> + u32 ecc_offset = mtd->writesize + FMC2_BBM_LEN;
> + u32 pcr = readl_relaxed(fmc2->io_base + FMC2_PCR);
> +
> + if (write_data)
> + pcr |= FMC2_PCR_WEN;
> + else
> + pcr &= ~FMC2_PCR_WEN;
> + writel_relaxed(pcr, fmc2->io_base + FMC2_PCR);
> +
> + /*
> + * - Set Program Page/Page Read command
> + * - Enable DMA request data
> + * - Set timings
> + */
> + csqcfgr1 = FMC2_CSQCFGR1_DMADEN | FMC2_CSQCFGR1_CMD1T;
> + if (write_data)
> + csqcfgr1 |= FMC2_CSQCFGR1_CMD1(NAND_CMD_SEQIN);
> + else
> + csqcfgr1 |= FMC2_CSQCFGR1_CMD1(NAND_CMD_READ0) |
> + FMC2_CSQCFGR1_CMD2EN |
> + FMC2_CSQCFGR1_CMD2(NAND_CMD_READSTART) |
> + FMC2_CSQCFGR1_CMD2T;
> +
> + /*
> + * - Set Random Data Input/Random Data Read command
> + * - Enable the sequencer to access the Spare data area
> + * - Enable DMA request status decoding for read
> + * - Set timings
> + */
> + if (write_data)
> + csqcfgr2 = FMC2_CSQCFGR2_RCMD1(NAND_CMD_RNDIN);
> + else
> + csqcfgr2 = FMC2_CSQCFGR2_RCMD1(NAND_CMD_RNDOUT) |
> + FMC2_CSQCFGR2_RCMD2EN |
> + FMC2_CSQCFGR2_RCMD2(NAND_CMD_RNDOUTSTART) |
> + FMC2_CSQCFGR2_RCMD1T |
> + FMC2_CSQCFGR2_RCMD2T;
> + if (!raw) {
> + csqcfgr2 |= write_data ? 0 : FMC2_CSQCFGR2_DMASEN;
> + csqcfgr2 |= FMC2_CSQCFGR2_SQSDTEN;
> + }
> +
> + /*
> + * - Set the number of sectors to be written
> + * - Set timings
> + */
> + csqcfgr3 = FMC2_CSQCFGR3_SNBR(chip->ecc.steps - 1);
> + if (write_data) {
> + csqcfgr3 |= FMC2_CSQCFGR3_RAC2T;
> + if (chip->chipsize > SZ_128M)
> + csqcfgr3 |= FMC2_CSQCFGR3_AC5T;
> + else
> + csqcfgr3 |= FMC2_CSQCFGR3_AC4T;
> + }
> +
> + /*
> + * Set the fourth first address cycles
> + * Byte 1 and byte 2 => column, we start at 0x0
> + * Byte 3 and byte 4 => page
> + */
> + csqar1 = FMC2_CSQCAR1_ADDC3(page);
> + csqar1 |= FMC2_CSQCAR1_ADDC4(page >> 8);
> +
> + /*
> + * - Set chip enable number
> + * - Set ecc byte offset in the spare area
> + * - Calculate the number of address cycles to be issued
> + * - Set byte 5 of address cycle if needed
> + */
> + csqar2 = FMC2_CSQCAR2_NANDCEN(fmc2->cs_sel);
> + if (chip->options & NAND_BUSWIDTH_16)
> + csqar2 |= FMC2_CSQCAR2_SAO(ecc_offset >> 1);
> + else
> + csqar2 |= FMC2_CSQCAR2_SAO(ecc_offset);
> + if (chip->chipsize > SZ_128M) {

Can you use

if (chip->options & NAND_ROW_ADDR_3)

instead?

> + csqcfgr1 |= FMC2_CSQCFGR1_ACYNBR(5);
> + csqar2 |= FMC2_CSQCAR2_ADDC5(page >> 16);
> + } else {
> + csqcfgr1 |= FMC2_CSQCFGR1_ACYNBR(4);
> + }

[...]

> +
> +void stm32_fmc2_write_data(struct nand_chip *chip, const void *buf,
> + unsigned int len, bool force_8bit)
> +{
> + struct stm32_fmc2 *fmc2 = nand_get_controller_data(chip);
> + void __iomem *io_addr_w = fmc2->data_base[fmc2->cs_sel];
> + const u8 *p = buf;
> + unsigned int i;
> +
> + if (force_8bit)
> + goto write_8bit;
> +
> + if (IS_ALIGNED(len, sizeof(u32))) {
> + const u32 *p = buf;

I'm pretty sure the framework provides no alignment guarantee on buf.
You'd better assume buf might not be aligned on 32 or 16 bits.

> +
> + len /= sizeof(u32);
> + for (i = 0; i < len; i++)
> + writel_relaxed(p[i], io_addr_w);
> + return;
> + }
> +
> + if (chip->options & NAND_BUSWIDTH_16) {
> + const u16 *p = buf;
> +
> + len /= sizeof(u16);
> + for (i = 0; i < len; i++)
> + writew_relaxed(p[i], io_addr_w);
> + return;
> + }
> +
> +write_8bit:
> + for (i = 0; i < len; i++)
> + writeb_relaxed(p[i], io_addr_w);

Is 8bit access really enforced by the byte accessor? In this case, how
can you be sure 32-bit accesses are doing the right thing? Isn't there
a bit somewhere in the config reg to configure the bus width?

> +}

Regards,

Boris

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